Facsimile transmission and reception of documents can be performed at the present time in accordance with two different procedures.
The first procedure consists in using a standard commercial facsimile unit which remains on permanent standby for calls and automatically prints any received copy. It is also capable of transmitting documents from a built-in reading system. This type of apparatus, however, is attended by the following disadvantages :
This is a dedicated machine which therefore does not permit reprocessing of computerized data transmitted or received in any data-processing system.
The quality of printing of received copy is limited to that of a thermal print commonly employed in all dedicated facsimile units.
By reason of its manual operation, it is impossible to create automatic systems for sharing this machine between a number of users without obliging them to wait until the machine is free before in turn being able to transmit their document.
The second procedure consists in using a microcomputer in which is inserted a facsimile card associated with a facsimile management package and connected to a printer via a series or parallel interface.
This procedure is also subject to appreciable drawbacks. In the first place, it makes use of an internal connector of the microcomputer at the expense of other extension cards and implies in addition that the microcomputer should be allowed to operate continuously in order to permit facsimile reception at each instant. However, continuous operation of the microcomputer may present problems of reliability, especially in the presence of hard disks containing important data.
In the second place, this procedure neutralizes part of the microcomputer resources. In fact, the associated package is very often multi-task so as not to convert the microcomputer to a dedicated machine, which would considerably limit the advantage of this solution. This package necessarily consumes a substantial part of the computing power of the microcomputer processor both in order to manage the multitask aspect but also, at the time of reception of facsimile documents, in order to manage the different protocols and to store all the data on disks. Furthermore, a multi-task package of this type requires a large memory capacity, thus making this solution much more costly and difficult to implement by reason of the various technical constraints in regard to memory utilization which are imposed by current processing systems.
Finally, printing of received or transmitted facsimile documents can be performed only by means of the printer which is connected to the microcomputer. The low bit rate of the interfaces commonly employed (300,000 bits per second in the case of the parallel interfaces, 115,000 bits per second in the case of the series interfaces), associated with the above-mentioned limitations of the software package results in particularly long printing times which may amount to several tens of minutes in the case of a series connection.